The present invention provides oxazinoquinolone derivatives having a ring connecting position 4 (N-4) and position 11 (C-11), and more specifically, provides compounds of formula (I) described herein below. These compounds are useful as antiviral agents, in particular, as agents against viruses of the herpes family.
The herpesviruses comprise a large family of double stranded DNA viruses. They are also a source of the most common viral illnesses in man. Eight of the herpes viruses, herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella zoster virus (VZV), human cytomegalovirus (HCMV), epstein-Barr virus (EBV), and human herpes viruses 6, 7, and 8 (HHV-6, HHV-7, and (HHV-8), have been shown to infect humans.
HSV-1 and HSV-2 cause herpetic lesions on the lips and genitals, respectively. They also occasionally cause infections of the eye and encephalitis. HCMV causes birth defects in infants and a variety of diseases in immunocompromised patients such as retinitis, pneumonia, and gastrointestinal disease. VZV is the causative agent of chicken pox and shingles. EBV causes infectious mononucleosis. It can also cause lymphomas in immunocompromised patients and has been associated with Burkitt""s lymphoma, nasopharyngeal carcinoma, and Hodgkins disease. HHV-6 is the causative agent of roseola and may be associated with multiple sclerosis and chronic fatigue syndrome. HHV-7 disease association is unclear, but it may be involved in some cases of roseola. HHV-8 has been associated with Karposi""s sarcoma, body cavity based lymphomas, and multiple myeloma.
Due to the unique position of chloro substitutent on the N-phenylmethyl of formula I described herein below, compounds of the present invention demonstrate unexpected activity against the above reference herpesviral infections, particularly, human cytomegaloviral infection.
U.S. Pat. No. 5,792,774 discloses oxazino 1,4-dihydro-4-oxoquinolines useful for the treatment of a large number of diseases modulated by tissue necrosis factor (TNF) or phosphodiesterase IV, including cytomegalovirus (CMV) infections.
U.S. Pat. No. 4,847,373 discloses 1,8-bridged 4-quinoline-3-carboxylic acids useful as antibacterial agents.
U.S. Pat. No. 5,583,135 discloses heterotricyclic derivatives having a strong immunomodulating activity, anti-inflammatory activity and anti-cancer activity.
The abstract of Japanese Patent JP 10324631-A discloses IgE antibody production inhibitor comprise a pyrido(1,2,3-de1,4-benzoxazine or a pyrido (1,2,3-de)-1,4-benzothiazine derivative.
The present invention provides a compound of formula I, 
wherein R1 is C1-6 alkyl, optionally substituted with xe2x80x94OH, xe2x80x94OC1-4 alkyl or het;
wherein C1-6 alkyl is optionally partially unsaturated;
wherein het is a radical of a five- or six-membered heterocyclic ring having one or two heteroatoms selected from the group consisting of oxygen, sulfur and N; or a pharmaceutically acceptable salt, racemate, solvate, tautomer, optical isomer or prodrug derivative thereof.
In another aspect, the present invention also provides:
a pharmaceutical composition comprising a compound of formula I, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable excipient (the composition preferably comprises an effective antiviral amount of the compound or salt),
a method of treating or preventing a herpesviral infection, comprising administering to a mammal (e.g. a human) in need of such treatment, a compound of formula (I) or a pharmaceutically acceptable salt thereof,
a compound of formula (I) or a pharmaceutically acceptable salt thereof for use in medical treatment (e.g. the treatment or prevention of a herpesviral infection),
the use of a compound of formula (I) or a pharmaceutically acceptable salt thereof to prepare a medicament for treating or preventing a herpesviral infection in a mammal (e.g. a human), and
a method for inhibiting a viral DNA polymerase, comprising contacting (in vitro or in vivo) the polymerase with an effective inhibitory amount of a compound of formula I, or a pharmaceutically acceptable salt thereof.
The invention also provides novel intermediates and processes disclosed herein that are useful for preparing compounds of formula I.
For the purpose of the present invention, the carbon atom content of various hydrocarbon-containing moieties is indicated by a prefix designating the minimum and maximum number of carbon atoms in the moiety, i.e., the prefix Ci-j indicates a moiety of the integer xe2x80x9cixe2x80x9d to the integer xe2x80x9cjxe2x80x9d carbon atoms, inclusive. Thus, for example, (C1-3)alkyl refers to alkyl of one to three carbon atoms, inclusive, or methyl, ethyl, propyl and isopropyl, straight and branched forms thereof.
The compounds of the present invention are named according to the IUPAC or CAS nomenclature system.
The term xe2x80x9cC1-6xe2x80x3, xe2x80x9d refers to an alkyl group having one to six carbon atoms such as, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, and their isomeric forms thereof.
A 5- or 6-membered heterocyclic ring includes pyridinyl, morpholinyl, thiomorpholinyl, piperazinyl, imidazolyl, or pyrrolyl.
Compounds of the present invention may be in a form of pharmaceutically acceptable salts.
xe2x80x9cPharmaceutically acceptable saltsxe2x80x9d refers to those salts which possess the biological effectiveness and properties of the parent compound and which are not biologically or otherwise undesirable.
Compounds of the invention may have a chiral center and be isolated in optically active and racemic forms. It is to be understood that the present invention encompasses any racemic, optically-active, polymorphic, tautomeric, or stereoisomeric form, or mixture thereof.
Specific and preferred values listed below for radicals, substituents, and ranges, are for illustration only; they do not exclude other defined values or other values within defined ranges for the radicals and substituents
Specifically, C1-6 alkyl can be methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl, 3-pentyl, hexyl, or heptyl; het can be pyrrolidino, piperidino, morpholino, thiomorpholino, or piperazine.
A specific value for R1 is C1-6 alkyl, which may be partially unsaturated and is optionally substituted by hydroxy or het.
A specific value for R1 is propyl.
A specific value for R1 is 3-hydroxypropyl.
A specific value for R1 is 3-hydroxy-1-propynyl.
A specific value for R1 is 4-morpholinylmethyl.
Examples of the present invention are:
a. N-(4-Chlorobenzyl)-9-(4-morpholinylmethyl)-7-oxo-2,3-dihydro-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxamide,
b. N-(4-Chlorobenzyl)-9-(3-hydroxy-1-propynyl)-7-oxo-2,3-dihydro-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxamide,
c. N-(4-Chlorobenzyl)-9-(3-hydroxypropyl)-7-oxo-2,3-dihydro-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxamide, or
d. N-(4-Chlorobenzyl)-7-oxo-9-propyl-2,3-dihydro-7H-[1,4]oxazino[2,3,4-ij]quinoline-6-carboxamide.
The following Charts A-B describe the preparation of the compounds of formula I of the present invention. All of the starting materials are prepared by procedures described in these charts, by procedures well known to one of ordinary skill in organic chemistry or can be obtained commercially. All of the final compounds of the present invention are prepared by procedures described in these charts or by procedures analogous thereto, which would be well known to one of ordinary skill in organic chemistry. All of the variables used in the charts are as defined below or as in the claims.
In Chart A, acid A-1,3-hydroxy-4-nitrobenzoic acid, is reacted with thionyl chloride to give the corresponding acid chloride, which is then treated with morpholine to provide amide A-2. Alkylation of the phenolic hydroxyl group is accomplished using methyl bromoacetate and potassium carbonate in refluxing acetone to give A-3. Reduction of the nitro group using hydrogen gas and catalytic palladium, followed by thermal cyclization of the intermediate amino ester, provides lactam A-4. Reduction of the lactam with lithium aluminum hydride affords amine A-5. Reaction of the amine with diethyl ethoxymethylenemalonate provides A-6, which is heated with polyphosphoric acid or a solution of phosphorus pentoxide in methanesulfonic acid, effecting cyclization to tricyclic ester A-7. Aminolysis of the ester using p-chlorobenzylamine at 150xc2x0 C. provides amide A-8. 
In Chart B, deprotonation of B-1, 3,4-difluoroiodobenzene, with lithium diisopropylamide in tetrahydrofuran, followed by quenching of the anion with carbon dioxide, provides regioisomeric mixture of acids B-2. Activation of the acid mixture with carbonyldiimidazole, followed by reaction of the imidazolide with ethyl trimethylsilyl malonate in the presence of base affords the single xcex2-ketoester B-3. Sequential treatment of the xcex2-ketoester with triethyl orthoformate and ethanolamine affords compound B-4, which is cyclized using potassium carbonate in DMF to provide tricyclic ester B-5. Aminolysis of the ethyl ester using p-chlorobenzylamine furnishes amide B-6, which is converted to alkynol derivative B-7 by palladium (II) catalyzed coupling of the iodide with propargyl alcohol. Catalytic hydrogenation of the alkyne using hydrogen gas and platinum on carbon provides hydroxypropyl compound B-8 and n-propyl analogue B-9. 
It will be apparent to those skilled in the art that the described synthetic procedures are merely representative in nature and alternative synthetic processes are known to one of ordinary skill in organic chemistry.
The compounds of the present invention and pharmaceutically acceptable salts thereof are useful as antiviral agents. Thus, these compounds are useful to combat viral infections in animals, including man. Specifically, these compounds have anti-viral activity against the herpes virus, cytomegalovirus (CMV). These compounds are also active against other herpes viruses, such as the varicella zoster virus, the Epstein-Barr virus, the herpes simplex virus, and the human herpes virus type 8 (HHV-8).
Also, while many of the compounds of the present invention have shown activity against the CMV polymerase, these compounds may be active against the cytomegalovirus by this or other mechanisms of action. Thus, the description below of these compounds"" activity against the CMV polymerase is not meant to limit the present invention to a specific mechanism of action.
The compounds of the present invention have shown activity in one or more of the assays described below. All of these assays are indicative of a compound""s activity and thus of its use as an anti-viral agent.
The HCMV polymerase assay is performed using a scintillation proximity assay (SPA) as described in several references, such as N. D. Cook, et al., Pharmaceutical Manufacturing International, pages 49-53 (1992); K. Takeuchi, Laboratory Practice, September issue (1992); U.S. Pat. No. 4,568,649 (1986); which are incorporated by reference herein. Reactions are performed in 96-well plates. The assay is conducted in 100 xcexcl volume with 5.4 mM HEPES (pH 7.5), 11.7 mM KCl, 4.5 mM MgCl2, 0.36 mg/ml BSA, and 90 nM 3H-dTTP. Assays are run with and without CHAPS, (3-[(3-Cholamidopropyl)-dimethylammonio]-1-propane-sulfonate) at a final concentration of 2 mM. HCMV polymerase is diluted in enzyme dilution buffer containing 50% glycerol, 250 mM NaCl, 10 mM HEPES (pH 7.5), 100 xcexcg/ml BSA, and 0.01% sodium azide. The HCMV polymerase, which is expressed in recombinant baculovirus-infected SF-9 cells and purified according to literature procedures, is added at 10% (or 10 xcexcl) of the final reaction volume, i.e., 100 xcexcl. Compounds are diluted in 50% DMSO and 10 xcexcl are added to each well. Control wells contain an equivalent concentration of DMSO. Unless noted otherwise, reactions are initiated via the addition of 6 nM biotinylated poly(dA)-oligo(dT) template/primer to reaction mixtures containing the enzyme, substrate, and compounds of interest. Plates are incubated in a 25 C or 37 C H2O bath and terminated via the addition of 40 xcexcl/reaction of 0.5 M EDTA (pH 8) per well. Reactions are terminated within the time-frame during which substrate incorporation is linear and varied depending upon the enzyme and conditions used, i.e., 30 min. for HCMV polymerase. Ten xcexcl of streptavidin-SPA beads (20 mg/ml in PBS/10% glycerol) are added following termination of the reaction. Plates are incubated 10 min. at 37 C, then equilibrated to room temperature, and counted on a Packard Topcount. Linear regressions are performed and IC50""s are calculated using computer software.
A modified version of the above HCMV polymerase assay is performed as described above, but with the following changes: Compounds are diluted in 100% DMSO until final dilution into assay buffer. In the previous assay, compounds are diluted in 50% DMSO. 4.5 mM dithiotherotol (DTT) is added to the polymerase buffer. Also, a different lot of CMV polymerase is used, which appears to be more active resulting in a more rapid polymerase reaction. Results of the testing of compounds of the present invention in this assay are shown in Tables 1 below. Other viral polymerase assays are performed using procedures similar to those described above.
These compounds of the present invention are administered in a pharmaceutical composition containing the compound in combination with a suitable excipient, the composition being useful in combating viral infections. Pharmaceutical compositions containing a compound appropriate for antiviral use are prepared by methods and contain excipients which are well known in the art. A generally recognized compendium of such methods and ingredients is Remington""s Pharmaceutical Sciences by E. W. Martin (Mark Publ. Co., 15th Ed., 1975), which is hereby incorporated by reference herein.
The compounds of the present invention are administered parenterally (for example, by intravenous, intraperitoneal or intramuscular injection), topically, orally, or rectally, depending on whether the preparation is used to treat internal or external viral infections.
For internal infections, the compositions are administered orally or parenterally at dose levels, calculated as the free base, of about 0.1 to 300 mg/kg, preferably 1.0 to 30 mg/kg of mammal body weight, and are used in man in a unit dosage form, administered one to four times daily in the amount of 1 to 1000 mg per unit dose.
For parenteral administration or for administration as drops, as for eye infections, the compounds are presented in aqueous solution in a concentration of from about 0.1 to 10%, more preferably about 0.1 to 7%. The solution may contain other ingredients, such as emulsifiers, antioxidants or buffers.
The exact regimen for administration of the compounds and compositions disclosed herein will necessarily be dependent upon the needs of the individual subject being treated, the type of treatment and, of course, the judgment of the attending practitioner.
The symbol xe2x80x9c--xe2x80x9d refers to the data are not determined.